On Wednesday evening, after Nicaraguan President Daniel Ortega launched his latest diplomatic salvo at Costa Rica over “reclaiming” the northwestern province of Guanacaste, the Costa Rican Foreign Ministry replied with a formal complaint, according to the ministry’s website.

On Wednesday afternoon the administration of Costa Rican President Laura Chinchilla consulted with Costa Rica’s ambassador in Managua, Javier Sancho, after Ortega threatened to appeal to the International Court of Justice at The Hague to recover Guanacaste, annexed to Costa Rica in 1824.

In the letter, Foreign Minister Enrique Castillo said Costa Rica viewed the declaration as a poor-faith provocation and that it “severely damaged relations” between both countries.

“My country and my government deplore this new offensive attitude from Nicaragua, based on a policy of rejection and disrespect of the 1858 Border Treaty, which the country flaunts through its occupation and claim on the Costa Rican territory of Isla Portillos [near the northeastern Caribbean coast], and the violation of the perpetual rights to Costa Rican free navigation of the San Juan River, among others.

“Threats like those yesterday [Tuesday] against the integrity and sovereignty of Costa Ricans not only violate the Cañas-Jerez Border Treaty of 1858 but also the principles of international law, like respect for territorial integrity and the stability of frontiers, and profoundly damage the historical ties shared by our two nations, and deeply aggravate the pending disputes between us,” reads the letter, according to the ministry’s press release.

Chinchilla responded in a statement that Ortega’s actions were “difficult to comprehend especially because Costa Rica is doing nothing to provoke these kinds of responses. Our obligation as the government is to […] give it all the attention that it deserves when one country threatens another with severing an important portion of its territory.”

Marco Antonio Jiménez Muñoz, the mayor of Nicoya, Guanacaste, the seat of the 1824 annexation, wrote a letter to Ortega that the statement was an “act of absolute ignorance” and underlined the “deep pride” guanacastecos feel in “belonging to the Republic of Costa Rica by our own choice.”

This latest spat marks a new low for the diplomatic relations between the two countries. Costa Rica recently filed a complaint with the world court over Nicaragua’s decision to send students to the disputed Isla Calero, also known as Isla Portillos, in apparent violation of the tribunal’s request that both countries vacate the wetlands.